Laminated light polabizer



Sept. Z, 1941. L Re 21,904

' -LAMINATED LGH' POLARIZER Original Filed A u 15, 1936 NVENTOR ATTORNEYReisued Sept. 23, 1941 v LAMINATED GET Edwin E. Land. Boston, Masa.,asior, by meme inmentsg to Polaroid Corporation. Dover, Del.. aoo-poratlon of Delaware Original No. amazzo, dated Amt Lasse; se. risiNo. 90,190, August s, sas; Application to: reisse na; 1940. se- No.saose 4 13 Ciaims. r .(01. 88-65) This invention relates to a new andimproved laminated light-poiarlzer.

An object oi' the invention is to provide a lisht-polarizer in laminatedform comprising a sheet-like light-polarizing element'having adhesivelyafllxed thereto a plurality of sheets of glass or other protectivemedia.

Another' object of the invention is to provide such a light-polarizerwherein the sheet-like light-polarizing element may comprise a 'setplastic having dispersed and embedded therein a multiplicity ofpolarizing particies oriented with their :polarizing axes in substantialparallelism.

Further objects of the invention are to provide a laminated polarizingelement wherein such a set plastic polarizer is adhesively aflixed totwo sheets oi' siass' by means of an adhesive comprlsing a substantialamount of plasticizer as compared with the plasticizer in the polarizingpl-astic; to provide such a lamination wherein a different -plasticizeris used in the cement from that employed in the polarizer; toprovidesuch a lamination wherein the index oi' refraction of the adhesivecoincides with that of the set plastic polarizer; and to'provide such alamination wherein the adhesive is a non-solvent 'of theplastic'polarizer.

A still further object of the invention is to provide a laminatedpolarizer comprising succes- `sive1y a sheet of glass; an adhesivecontaining a large; amount of plasticizing material, a sheet oflight-polarizing material comprising` a set plastie and a minimum ofplasticizing material, a second layer oi' adhesive comprising a largeamount of plasticizing material, and -a second sheet of glass.

A still further 'object of 'the invention is to provide a laminatedlight-polarizing element possessing a maximum of shatter-prooiproperties.

, Other objects of the invention will in part be obvious and will inpart appear hereinater.

The invention accordingly comprises the article possessing the features,properties, and the relation of elements which are exemplifled in thefollowing detailed disclosure, and the scope of the application of whichwill be indicated in the claims.

For a -iuller understanding of the nature andobjects of the inventionreference should be had to the accompanying drawing. which represents inan enlarged and somewhat dia"grammatic view a cross-section o! alaminated polarizlng element embodying the presentainvention. y

The present invention contemplates the production oi a laminatedlight-polarizing material comprising essentially a central layer oflightpoiarizing material in sheet-like for-m. two outer layer-s of glassor other like material, and intermediate layers` of adhesive adapted tojoin permanently the polarizing layer to the outer layers of glass orother material. I

The polarizing material employed may comprise a material soldcommercially under the trade-name "Polarioid." This material comprises aset plastic medium having embedded therein a' mass of polarizingparticles such, for example, as particles of herapathite, with theirpolarizing axes oriented to substantial paralielism. The materialpossesses certain distinct advantages. It may be obtained in sheet-likeform,

the sheets are thin, pliable, easily shipped and' handled, and they maybe cut to any desired size. The material possesses an unlimited-angularaperture and is highly efllcient as a lightpola-izer.

` Where Polaroidis employed as the sheet-like polarizing material in thelamina'tion of the pres- -ent invention, the adhesive should comprise aplastlcizer which does not deleteriously aflect the crystals ofherapathite or which is not a solvent for cellulose acetate, celluloseacetate .being the material employed esthe transparent suspending mediumin Polaroid.

It is to be understood that while Polaroid is a preferred polarizingmaterial, other suitable materials may. if desired, be employed. In/every case, however, the adhesive employed in the present inventionshould preierably contain a plasticizer which is either inert in thequantities used, with respect to the polarize', or which is a nonsolventfor the polarizer.

Where Polaroid is employed the suitable adhesive may comprise a mixtureof a highly polymerized vinyl acetate, such as the material soldcommercially as Vlnylite Als," and dibutylphthalate, in' the proportionapproximately of 300 grams of vinyl acetate to 100 cc. ofdibutylphthalate. In such a mixture dibutyl-phthalate acts as theplasticizer' and is a'non-solvent for cellulose acetate. such acementitious material may also function as a water-prooflng 'agent..

The mixture of Vinyiite and dibutyl-phthalate may preferably .beheatedto a temperature approximately of 250 F., and may be cooked at thattemperature for a period .ot from two to three hours. It is to beunderstood, however, that these temperatures and periods of time are notcritical, but that the materials should be mixed and heated until theyare thoroughly plas- !orced !rom the gun on to the glass 'sheetsemployed in the manutacture ot the laminated polarizer; I! desired theprepared adhesive mixture may be extruded or otherwise !ormed into thinsheets. which may be cut to size and placed upon suitable glass sheets.I

It is to be understood that the adhesive is preferably applied to twosheets o! siass or similazmaterial which, 'during this stage of theprocess, may be maintained ata temperature oi' approximately212 I". Hereagain the temperature is by no means critical. It is. preterable to workthis stage of the process with the materials in heated condition, sothat they may be maintained in a fairly plastic condition. I! desired,however, the adhe'sive may be applied cold to the glass and the glassand adhesive then heated.

The sheet-like 'polariaing material, suitably cleaned, may then beapplied to the adhesive on one o! the giass plates, and the other plateplaced on top ol' the polarizing sheet and the assembiy then placed inany suitable press or other holding mechanism, and subiected to auniform pressure, preierably in the nelghborhood oi 150 to 200 poundsper square inch and !or a. period oi' from one to two minutes. Hereagain the pressure employed and the 'time during which the pressure maybe applied are not critical. If a smaller pressure is employedit will beunderstood that the lamination will be held under the pressure !or asomewhat higher period. Throughout the period of pressing it ispreferable to maintain the lamination at a temperature, for example, ofi'rom 200 to-2l2 I". 'The lamination is then removed from the press andthe extruded adhesive rolled or cut from around the edges of thelamination. The entire assembly is then suitably cleaned.

In the drawing, III represents the glass plates..

ll the layers of adheslve, and 12 the lightpolarizing material.

While a mixture oi' Vinylite, and dibutyl- *phthalate has been describedas the preferred cementing material, it is to be understood `that othermaterials may be employed. For example, other vinylcompounds may beemployed, or an acrylic' ac'id .ester may be employed as the adhesivewith suitable plasticizing media. Even where Vinylite is employed it isto be understood that other plasticizers -may be employed, provided,however, that the plasticizer is a non-solvent tor the polarizingmaterial in the 'laminatiom The index of rel'raction for Polaroid which.it'

the present invention. Il' it is desired, howu ever, to change theplastlcizing material and still to employ Vinylite in the .cement. otherpla'stics suitable to the present invention maybe diethyl-phthalate orisoamyl-phthalate.

While glass has been. described as the medium employed in 'connectionwith the laminatlon oi, the present invention. it is to be understoodthat other media may be employed as the outer or protective elements.For example' synthetic plastics such as the material sold as "Plexigum,"

a polymerized acrylic acid ester, or.sheet cel- I lulosic compounds, orother similar media may be employed. It is to be understood that wheremedia other than glass are employed it may be desirable to supply acementitiojis material which may be plastic at lower temperatures thanthat of the cement described in connection with the preferred embodimentof the invention above.

It is also to be understood that, it desired, a single layer of adhesivemay be employed to afflx the polarizing element to a supporting mem--'to employ a somewhat harder cement than that described above,tor-example a cement whereln less plasticizer' is employed. Where thismodification of the process is employed it is to be understood that theprepared 'sheets of light-polarizing material employed with thecementitious coating applied ther'eto 'maybe kept 'available forlamlnation with glass or other material ove 'a somewhat extended period.

It is to be understood furthermore that under certain circumstances itmay be deslrable to employ Canada balsam as the cement; This material isnot, however, to be preferred. It is ex- 'pensive and possesses a distinctive yellowish color. It has the advantage, however, of being harderthan the cement 'described in connection with the preferred embodimentof the invention when cold and' somewhat more easily rendered Dlasticwhen'heated. Canada balsam is, 'however, not useful where shatter-prooi'properties are to be desired. i i

The lamination ot-the? preferred embodiment` of the invention describedabove possesses very excellent' 'shatter-prooi' properties, i. e.shatterprooi! inthe sense used in the` automotive windshield industry.Polaroid, which' is ordinarily employed'as' the preferredlight-polarizing material, usually contains very little plasticizer andhence possesses' great tensile `strength.` The cement material describedabove maintains a very fine bond between the light-polarizing materialand the' giass over-a wide range of temperature variations. r

Where desired the product of the present invention may be produced inrelatively thin form. For example, the glass or other material employedas the cover plates need only be thick enough to resist breakage underthe pressures employed in the preparation of the lamination. Thellght-polarizing sheet need be-no thicker than, !or example, .005 of aninch, and the layers o! adhesive may be even thinner.

Since certain changes may be made in the above product and differentembodiments oi' the invention could be made-without departing :rom the:cope thereoi, itis intended that all matter contained' in the abovedescription or shown 'in the, accompanying drawing shall be interpretedas illustrative andnot in a limiting sense.

It is also to be understood that the following claim: are intended tocover al otthe generic a and specific features oi the invention hereindescribed, and all statements oi the sccpe oi' the invention which. as amatter of language, might be said to fall therebetween. a

Having described my invention, what I claim as'new and desire to secureby Letters Patent is:

1. A lamination comprising a plurality oi transparent elements havingsandwiched therebetween and bonded thereto a sheet-like light-polarizingbody comprising a set suspending medium having a mass ot orientedpolarizing particles embedded therein, the lamination also comprisingbonding material having a substantially higher plasticizer contentthansaid set suspending medium and being substantially inert withrespect to said light-polarizing` body.

2. A lamination comprising a plurality ot trans-` parent elements havingsandwiched therebetween and bonded thereto a sheet-like light-polarizingbody comprising a set suspending medium having a mass' ot orientedpolarizing particles embedded therein,-the lamination also comprisingbonding material, said material being substantially inrt with respect tosaid light-polarizing body and having an index of retraction coincidingsubstantially with that oi' said set suspending medium.

3. A lamination comprising a plurality oi' transparent elements havingsandwiched therebetween a sheet-like light-polarizing body comprising aset suspending medium having a mass oi oriented polarizing particlesembedded therein, and means tor cementing said light-polarizing body tosaid layer comprising a highly polymerized vinyl compound and arelatively large amount of plasticizer, a light-polarizing layercomprising a set suspension o! oriented polarizing particlea in acellulosic medium comprising a relatively small amount oi plasticizer, asecond adhesive layer and a second glaas sheet, the plasticizer in saidadhesive bein a non-solvent otsaid ,celiulosic medium and ot saidpolarizing particles.

8. A lamination comprising a plurality of transparent elements havingsandwiched therebetween and bondedthereto a sheet oi plastic having arelatively low plasticizer content, the lamination 'also comprisingbonding material having a substantially higher plasticizer content thansaid plastic. 9. A lamination comprising a sheet oi giass, an

. adhesive having a relatively high plasticizer content; a sheet oitransparent plastic having a rela -tively low plasticizer content, anadhesive having a relativev high plasticizer content, and a second sheetot glass, the adhesive layer-s bonding the plastic to the sheets ofsiass.

10. A laminated plate ot non-glare safety giass comprising a pair oiglass sheets, a layer ot plasticized polymerized vinyi resin adhe-ent tothe inner face of each glass sheet, and a relatively thin sheet of hardcellulosic material'intermediate the vinyl resin layers and adheredthereto, the cellulosic material having dispersed and embedded therein amultipicity ot light polarizing particles with their polarizing axesoriented to substantial parallelism, the sheet ot cellulosic materialhaving relatively little 'plasticizer' as com-` pared with the layersoi' vinyl resin.

11. A laminated plate oi non-glare safety glass comprising a pair ofglass sheets. a layer oi' plastransparent elements, said meanscomprising a vinyl compound having a substantially higher plasticizercontent than said set suspending medium.

4. A sheet oi' light-polarizing material having each oi its iaces coatedwith a substantially waterprooi', transparent cement havingsubstantially the same index of reiraction as said sheet.

5. A shatter-prooi, light-polarizing lamination comprising a pluralityoi sheets ot glass, a sheet of light-polarizing material comprising aset plastic material and a minimum amount oi plasticizer, and a cementfor uniting said sheets comprising a plastic and a relatively largeamount oi plasticizer.

ticized polymerized vinyl resin adherent to' the inner face of eachglass sheet, and a relatively thin sheet of hard cellulosic materialintermediate the vinyl resin layers and adhered thereto, the cellulosic'material having dispersed and embedded therein a multiplicity oflight-polarizing particles with their polarizing axes oriented tosubstantial paralielism.

12. A iaminated plate of non-glare safety glass comprising a pair orglass sheets, a layer o! plasticized, polyme'rized vin'yl resin adherentto the 'inner face o! each glass sheet, and a relatively thin sheet of atransparent plastic intermediate the vinyl resin layers andadhered'thereto, said 6. A shatter-proor, light-polarizing lamination icomprising a plurality oi sheets of glass, a sheet of light-polarizingmaterial comprising a set plastic material and a minimum amount olplasticizer, and a cement !or uniting said sheets com aprising a vinylcompound and a relatively large amount oi plasticiser.

'7. In combination, a glass sheet, an adhesive sheet having dispersedand embedded therein a muitipiicity of light-polarizing particles withtheir polarizing axes orlented to substantial parallelism.

13. A lamination comprising a'plurality of transparent elements havingsandwiched therebetween and bonded thereto a sheet-like lightpolarizingbody comprising a set suspending medium having a mass of orientedpolarizing particles embedded therein, the lamination also com'- prisingbonding material comprising plasticized polymerized vinyl resin.

` EDWIN E. LAND.

